The major goals of the coming year are to evaluate the effects of direct manipulations of the GABA system in the medial hypothalamus on feeding behavior of rats. The main procedure to be used is the chronic infusion of GABA-transaminase inhibitors such as ethanolamine-o-sulfate. Subsequent studies will analyze the concurrent effects of these agents administered in conjunction with GABA receptor blocking agents and metabolic substrates such as glucose. The theoretical underpinning of the work is that metabolic information concerning past energy intake is encoded in hypothalamic feeding circuits via the entry of metabolic information via the GABA shunt. Substantial support for this principle has already been collected, and the present work is a continuation of that analysis. A subsidiary aim will be to characterize nutrient dispersion in the hypothalamus as a function of metabolic states. Experiments in this series consist of the autoradiographic analysis of brain tissue following administration of various isotope labelled nutrient loads. In the coming year, the major project will be to characterize the entry of glucose into the brain as a function of time since intragastric loading. These brain parameters will be correlated with concurrent behavioral studies analyzing the satiating effects of glucose administered in the same manner.